The present invention relates to a method and apparatus for applying a liquid to a substrate and, more particularly, to an automated method and apparatus for applying one or more liquids, including for example a primer coating or a treatment liquid, to a glass panel, such as a window assembly.
The recent trend in vehicles is to produce an aerodynamically shaped vehicle with larger windows to improve visibility. In order to reduce the aerodynamic drag and enhance the overall appearance, window assemblies are more recently mounted to the vehicle body by an adhesive, often in combination with one or more fasteners which are mounted to an inner surface of the window panel or are embedded in a gasket which has been previously extruded or molded on to the window panel after priming of the substrate surface. It has been found that the priming of the substrate surface improves the adhesion of the gasket to the substrate. The adhesive is applied to the surface of the panel or the gasket, for example by extrusion. To install, the window assembly is then pressed against the mounting flange or decking of the vehicle body to which the adhesive adheres after curing. In other windows, the securement of the window panel to the vehicle is achieved by a fastening system. In some fastening systems, the fastener is adhered directly to the surface of the window by an adhesive. Before applying such adhesives, the window panel is preferably treated with a treatment liquid, such as an acid solution or cleaning solution, to prepare the glass panel and improve the adhesion of the adhesive to the glass panel. In many windows, therefore, the adhesive often provides the primary attachment of the panel to the vehicle.
However, window assemblies often include compound curvatures, which make it hard to automate the application of the gasket primer or treatment liquid. In preferred forms, the primer or treatment liquid is directly applied to the window substrate rather than sprayed or wiped on in order to achieve a more uniform coverage and thickness. As a result of the compound curvatures and the irregularities in the surface topology of window panels, direct application of a primer or treatment liquid to a window assembly has been more typically accomplished manually with the use of an applicator.
Conventional applicators include a tip, for example a pad, including a felt pad, and a reservoir which holds a supply of the primer solution or treatment liquid. However, when applying a liquid that dries when exposed to air, such as most conventional primers, the pads of the applicators must be replaced frequently. For example, primers dry relatively quickly in ambient conditions and tend to harden the pad and clog up the applicator. As a result, applicator tips or pads require frequent replacement, and the applicator reservoir must be cleaned and flushed before refilling.
As described above, heretofore, manual application of the primer has been preferred due to the compound curvatures and irregularities in the surface topology of the window assembly substrate and more consistent results due to varying conditions of the substrate (i.e. frit, contamination, temperature, or the like). Furthermore, it has been found that in order to achieve optimal results, the liquid is preferably applied with a constant pressure so that a uniform coating can be achieved. Heretofore, this constant pressure has been easier to achieve with manual application. However, manual application may result in inaccurate primer or treatment liquid placement and the coating thickness may vary with each worker. Moreover, conventional primer systems are open systems which result in prolonged exposure of the primer to contaminants. Given the reactive nature of primer solutions, these open systems cause the primer solution to prematurely cure. Therefore, these open primer systems are wasteful and require frequent cleaning and or replacement of the applicators.
Consequently, there is a need for a liquid application system which will produce the same advantages of a manually applied coating system, including a substrate surface and substrate condition variation sensitive system, but will require less material usage and, consequently, produce less waste than a manual application process. Furthermore, there is a need for a liquid application system that will provide a longer life for the applicator tip. In addition, there is a need for a primer application system which can provide a highly accurate primer or treatment liquid placement and produce a repeatable coating thickness. Moreover, there is a need for a closed primer system which will reduce waste and increase the life of the applicator and further reduce contamination of the treatment liquid or primer solution.
The present invention provides a method and apparatus for applying a liquid, such as a treatment liquid or primer, to a substrate with an applicator assembly, which is responsive to variations in the characteristics and surface topology of the substrate. Preferably, the primer applicator assembly can apply the liquid to the substrate with a constant pressure so that the applied liquid will have a uniform shape and thickness. Furthermore, when used in a primer application process the present invention provides a liquid applicator system which prevents the premature hardening of the primer solution in the applicator and, consequently, increases the life of the applicator. Moreover, the primer applicator assembly permits automation of the liquid application process and, therefore, can provide a highly accurate coating placement and produce a repeatable application path and coating thickness. In addition, the applicator system provides a closed system that is particularly suitable for applying primers which eliminates or substantially reduces the contamination of the liquid and the amount of volatiles which escape from conventional primer solutions.
In one form, an applicator assembly for use in an automated liquid application system for applying a liquid to a substrate includes a base, which is adapted to be gripped by a holding member, and a liquid applicator. The applicator is moveably mounted on the base and is adapted to receive a supply of liquid and is positionable on the substrate by the holding member for applying the liquid to the substrate. The liquid applicator moves on the base to follow the contour of the substrate thereby applying constant pressure to the substrate during a liquid application process.
In one aspect, the base includes a pin, with the liquid applicator being slidably mounted on the base by the pin. Preferably, the liquid applicator is mounted on the pin by an adapter, which includes a transverse supply passage for receiving the liquid. The applicator is mounted to the adapter and is communication with the transverse supply passage for receiving the liquid. In further aspects, the adapter includes a liquid applicator fitting mounted thereon, with the applicator fitting including the liquid applicator. In another aspect, the applicator includes a mounting portion, a flange portion, and an applicator tip coupled to the flange portion. Preferably, the applicator fitting extends into the mounting portion of the liquid applicator and is coupled thereto by a friction fit so that the applicator is removably mounted to the applicator fitting. In preferred form, either the applicator fitting or the mounting portion includes an annular seal to provide a fluid type connection between the applicator fitting and the liquid applicator and, optionally, to provide the friction fit. In further aspects, the applicator tip preferably comprises a pad, for example a felt pad, which absorbs the liquid for directly applying the liquid onto the substrate.
In yet further aspects, the base includes a pair of flanges, which provide stops and limit the movement of the adapter between a first position and a second position along the pin. Optionally, the applicator assembly may further include a biasing member which is mounted on the pin and positioned between one of the flanges and the adapter to bias the applicator for contacting the substrate with a constant pressure, which is especially suitable for applications in which the substrate is vertically oriented.
In yet another aspect, the applicator assembly further includes a liquid supply line, which is coupled to the adapter and delivers liquid to the liquid applicator through the transverse supply passage. Preferably, the liquid supply line is coupled to the adapter by a supply line fitting, for example a male fitting.
In one aspect, the base is coded to uniquely identify the applicator assembly. For example, the base may be mechanically coded, such as by providing the base with a projecting rib. Furthermore, the base may include a second projecting rib for further providing mechanical coding of the applicator assembly. Alternately or in addition, the base may include one of a plurality of holes, a plurality of recesses, or a magnetic strip or strips or the like for coding the applicator assembly.
According to another form of the invention, an automated liquid applicator system for applying a liquid to a substrate includes a robot having a movable gripper and at least one liquid applicator assembly. The liquid applicator assembly includes a base and an applicator tip which is mounted to the base and which is adapted to receive a supply of liquid. The gripper holds the base and positions the applicator tip on the substrate for applying a liquid onto the substrate. Preferably, either the applicator assembly or the robot is adapted to apply constant pressure to the substrate during the application process.
In further aspects, the automated priming system includes a docking station. The docking station optionally includes a reservoir and a port in communication with the reservoir. When automated priming system is used for applying a primer, the reservoir holds a solvent for preventing premature hardening of the primer solution in the applicator tip. The robot positions the applicator tip in the port between applications of the primer solution onto the substrate, thereby extending the life of the applicator tip.
In yet further aspects, the applicator assembly is preferably adapted to apply a constant pressure to the substrate when the applicator tip applies the liquid onto the substrate. For example, the applicator tip may be movably mounted on the base, whereby the applicator tip follows the contours of the substrate which results in the applicator tip applying a constant pressure to the substrate. In further aspects, the applicator tip is slidably mounted on the base by a pin. Preferably, the applicator assembly includes an adapter which slidably mounts the applicator tip on the pin. The adapter includes a transverse supply passage for receiving the liquid, with the applicator tip being mounted to the adapter and being in communication with the transverse supply passage for receiving the liquid.
In another form, an automated priming system for applying a primer to a substrate includes a robot, a primer delivery system, at least one applicator assembly, and a docking station. The robot includes a movably arm and a gripper mounted to the movable arm. The applicator assembly includes a base and an applicator tip mounted to the base, with the applicator tip being adapted to receive a primer solution from the primer deliver system through a supply line. The gripper holds the base and positions the applicator tip on the substrate for applying the primer solution onto the substrate with one of the applicator assembly and the robot being adapted to apply constant pressure to the substrate with the applicator tip during a primer application process. The docking station includes a reservoir, which holds a solvent that prevents the primer solution from hardening, and a port, which is in fluid communication with the reservoir. The robot positions the applicator tip in the port of the reservoir between applications of the primer solution on to the substrate to prevent the primer solution in the applicator tip from hardening between applications.
In one aspect, the primer supply system includes a primer reservoir for holding a supply of primer solution and a delivery pump for delivering the primer solution to the applicator assembly through the primer supply line. For example, the delivery pump may comprise a peristaltic delivery pump. Preferably, the primer supply system includes a recirculating pump, which recirculates primer solution through the primer reservoir to maintain the homogeneous properties of the primer solution.
In further aspects, the automated priming system comprises a plurality of the applicator assemblies, with each of the applicator assemblies being coded to uniquely identify the respective applicator assemblies. Furthermore, the automated priming system preferably includes a corresponding plurality of primer supply systems, wherein each of the applicator assemblies is associated with a respective primer supply system.
According to yet another form of the invention, a method of applying a liquid to a substrate includes supporting a substrate, holding a liquid applicator assembly, which includes a liquid applicator and is adapted to apply a constant pressure to the substrate, positioning the liquid applicator assembly on the substrate, directing a liquid onto the substrate through the applicator assembly and liquid applicator, and storing the applicator assembly between applications in a fixed location.
In further aspects, the method includes coupling the applicator assembly to a primer supply system. Preferably, the primer solution is recirculated through the primer supply system to maintain the homogeneous properties of the primer solution. In one aspect, the method further includes storing the applicator assembly in an environment which prevents premature hardening of a primer solution in the applicator assembly.
In other aspects, the method includes providing a plurality of applicator assemblies and selecting one of the applicator assemblies for applying a first liquid solution to the substrate. Preferably, the applicator assemblies are coded whereby each applicator assembly is uniquely identifiable.
In yet other aspects, the method further provides a robot with a gripper, wherein the applicator assembly is held by the gripper of the robot. Further, the method includes providing a docking station with a reservoir and a port in fluid communication with the reservoir. A liquid primer solution solvent is held in the reservoir, which prevents premature hardening of a primer solution in the applicator. The applicator is stored in the port of the reservoir with the applicator being adjacent and engaging the solvent vapors but out of contact with the liquid solvent so that the primer solution in the applicator assembly does not prematurely harden.
The improved apparatus and method disclosed herein provides for an automated system of applying a liquid, such as a primer solution or a treatment liquid, to a substrate, for example a window assembly. The automated applicator system incorporates a liquid applicator assembly that is adapted to follow the contours of the substrate in order to apply a constant pressure to the substrate when applying the liquid. Furthermore, the automated system of the present invention optionally provides a closed loop system, thus, reducing waste and the risk of ambient contamination for the liquid, which is especially suitable for most conventional primer solutions. Moreover, the application system includes a docking system for holding the applicator assemblies in a fixed location and which optionally includes a reservoir for holding a primer solution solvent that prevents the applicable primer solutions in the applicator assemblies from prematurely hardening. In addition, in preferred form, the application system of the present invention utilizes a robot which is adapted to hold the applicator assemblies and provides a more accurate placement of the liquid on the substrate.